One by one, Iraqi cities seem to be falling to a militant group bent on continuing its march forward.

What's happening in Iraq now has all the makings of a civil war - and a full-blown foreign policy crisis. The United States is mulling direct talks with Iran while it boosts security at the U.S. Embassy in Baghdad with military personnel.

Why Iran? In recent days, Iran has sent hundreds of troops to fight alongside Iraqi government security forces in Diyala province, a senior security official in Baghdad told CNN.

Clearly, the crisis in Iraq is spilling far beyond its borders. Here's the latest:

Iraq's military strikes back at ISIS

After days of violent advances by the militant group ISIS, the Iraqi air force killed more than 200 militants from the Islamic State in Iraq and Syria, Iraqi state TV reported Monday.

The air raids against ISIS took place in Saqlawiya, northwest of Falluja, according to state TV.

ISIS has been fighting to take control of Iraq, seizing cities across the country.

Iran enters the mix

In recent days, Iran has sent about 500 Iranian Revolutionary Guard troops to fight alongside Iraqi government security forces in Iraq's Diyala province, according to a senior security official in Baghdad who spoke to CNN on Friday.

But Iranian President Hassan Rouhani denied reports that some of Iran's elite forces are in Iraq to help bolster Iraqi Prime Minister Nuri al-Maliki, a fellow Shiite.

"If the Iraqi government wants us to help, we will consider it," Rouhani said, according to an English translation of his remarks Saturday on state-run Press TV.

But "so far they have not asked specifically for help." Rouhani added that Iran could give strategic guidance if requested.

The Obama administration is exploring possible direct talks with Iran over the deteriorating situation in Iraq, two senior U.S. officials told CNN.

Both officials ruled out any type of teaming up with Iran because the United States and Iran don't have a lot of common interests - other than a stable Iraq.

The United States is wary of furthering Iran's already considerable influence in Iraq. The Shiite Iranian regime is al-Malaki's closest ally in the region. And the Obama administration is concerned appearing to team up with Iran would both alienate Iraq's Sunni majority and worry Sunni allies of the United States in the region.

Army Sgt. Bowe Bergdahl, the last American prisoner of war, returned home early Friday morning, his hero's welcome supplanted by a controversial prisoner swap and his reputation tarnished by accusations he was a deserter.

He arrived in San Antonio, Texas, from a military hospital in Landstuhl, Germany, where he'd been recuperating since his release May 31 in exchange for five Taliban figures held at Guantanamo Bay, Cuba.

The 28-year-old Bergdahl, the longest held American soldier since the Vietnam War, was taken to the San Antonio Military Medical Center.

"The Army will continue to ensure that Sgt. Bergdahl receives the care, time and space he needs to complete his recovery and reintegration," Pentagon spokesman Rear Adm. John Kirby said.

Bergdahl's full physical recovery may take months; his public rehabilitation will likely take longer.

The swap that freed Bergdahl has stirred up a political storm in Washington. And almost-daily revelations about Bergdahl's time in Afghanistan have not helped matters.

"Everybody has a piece of the story, and very few people have the whole story," a Defense Department psychologist told reporters.

The backlash has gotten so bad that a public celebration in his hometown of Hailey, Idaho - one that the 8,000 residents there had waited five years for - has been scrapped for fear of protests.

"It isn't over for us," Bergdahl's father, Bob, told reporters last week. "In many ways, it's just beginning for Jani and I, and our family. There's a long process here."

An audio recording purportedly from the Islamic State of Iraq and Syria promises more fighting in more Iraqi cities, including Baghdad.

"Continue your march as the battle is not yet raging," a voice said to be that of ISIS spokesman Abu Mohammed al-Adnani says on the message posted early Thursday (last Wednesday night ET) on the group's media website.

"It will rage in Baghdad and Karbala. So be ready for it."

CNN cannot confirm the authenticity of the audio or time and date of its recording, which is nearly 17 minutes long.

"Don't give up a hand's width of ground you've liberated," the voice says in apparent encouragement of ISIS fighters.

The message, if authentic, is further proof that the militant group are not content with control of the places they have already taken over - and are setting their sights higher.

In what's being called a political "earthquake," the No. 2 Republican in the House, Eric Cantor, lost his primary on Tuesday to a college professor and tea party neophyte.

Cantor conceded the race with 99% of precincts reporting from the Richmond-area district showing him trailing Dave Brat 56% to 44%, according to the Virginia Secretary of State's website. Turnout was low.

"Obviously we came up short," Cantor said in his concession speech.

"It's disappointing sure but I believe in this country. I believe there is opportunity around the next corner for all of us," said Cantor, whose loss is all the more shocking because he's considered very conservative.

In a statement following Cantor's defeat, House Speaker John Boehner called the No. 2 Republican "a good friend and a great leader."

In his victory speech, Brat struck a populist tone.

"Dollars do not vote, you do," he said. "When I go to D.C., every vote I take will move the pendulum in the direction of the people, away from Washington, D.C.; back to the states; back to the localities; and back to you."

Mark Preston, CNN's executive political editor, said the defeat would have national implications since Cantor has been viewed as ambitious and a potential speaker.

"This came out of nowhere," Preston said.

CNN Political Analyst David Gergen called it an "earthquake" that would "send shock waves through the Republican ranks."

It was not immediately clear how the militants were carrying out their attack or how many casualties may have resulted. At least 30 ambulances rushed to the scene, Mohsin said.

Late Sunday night, 10 militants stormed the same airport's cargo area, leading to an hours-long assault that left 36 people dead.

The Pakistani Taliban claimed responsibility for that assault, saying the attack was retaliation for the death of former chief Hakimullah Mehsud, who was killed in a U.S. drone strike in November in North Waziristan.

The militant group, also known as the TTP, had warned of more carnage starting Tuesday.

Shahidullah Shahid, another TTP member, said earlier this week that the group would engage "in a full-out war with the Pakistani state, starting on June 10."

But the airport itself is safe, Pakistan's Civil Aviation Authority said Tuesday.

U.S. President Barack Obama paid tribute Friday to the U.S. servicemembers who "defied every danger" to pour onto the beaches of Normandy 70 years ago in defense of liberty.

His remarks at the American Cemetery in Colleville-sur-Mer, which overlooks Omaha Beach where so many fell, are part of a series of solemn events to commemorate the D-Day landings in northern France.

Obama, who arrived with French President Francois Hollande, shook hands with elderly veterans before the presentation of colors and playing of the two countries' national anthems.

Obama said he was honored to be there "to pay tribute to the men and women of a generation who defied every danger: among them, our veterans of D-Day."

Lengthy applause rang out as the U.S. President said he was humbled by the presence of some of those veterans at the ceremony.

"Here, we don't just commemorate victory, as proud of that victory as we are; we don't just honor sacrifice, as grateful as the world is; we come to remember why America and our allies gave so much for the survival of liberty at this moment of maximum peril," Obama said.

The sense of pride expressed by officials of the Obama administration at the release of Army Sgt. Bowe Bergdahl is not shared by many of those who served with him - veterans and soldiers who call him a deserter whose "selfish act" ended up costing the lives of better men.

"I was pissed off then and I am even more so now with everything going on," said former Sergeant Matt Vierkant, a member of Bergdahl's platoon when he went missing on June 30, 2009. "Bowe Bergdahl deserted during a time of war and his fellow Americans lost their lives searching for him."

Vierkant said Bergdahl needs to not only acknowledge his actions publicly but face a military trial for desertion under the Uniform Code of Military Justice.

A reporter asked Defense Secretary Chuck Hagel Sunday whether Bergdahl had left his post without permission or deserted - and, if so, whether he would be punished. Hagel didn't answer directly. "Our first priority is assuring his well-being and his health and getting him reunited with his family," he said. "Other circumstances that may develop and questions, those will be dealt with later."

Following his release from five years of captivity in Afghanistan on Saturday, Bergdahl was transferred to a military hospital in Germany.

A senior Defense official said Bergdahl's "reintegration process" will include "time for him to tell his story, decompress, and to reconnect with his family through telephone calls and video conferences."

Said Bergdahl's former squad leader, Greg Leatherman: "I'm pleased to see him returned safely. From experience I hope that he receives adequate reintegration counseling. I believe that an investigation should take place as soon as healthcare professionals deem him fit to endure one."

Another senior Defense official said Bergdahl will not likely face any punishment. "Five years is enough," he told CNN on condition of anonymity.